U.S. application Ser. Nos. 08/010,092 and 08/010,081, filed Jan. 27, 1993, both of which are assigned to the same assignee as the present application, disclose a data management system for transport refrigeration units, such as refrigeration units for straight trucks, tractor-trailer units, containers, and the like. The disclosed data management system has distributed control and a communications protocol which is particularly suited for accurately exchanging large amounts of data between the nodes of the communication system.
One of the nodes illustrated in the above mentioned patent applications is a data logger node which stores information relative to predetermined variables during the operation of an associated transport refrigeration unit. If would be desirable, and it is an object of the invention, to provide a new and improved method of logging such operational data which facilitates retrieval of the information in various formats, including data relative to a specific trip of the transport refrigeration unit, and data relative to all of the trips having information stored in the data logger. The various formats should also include the ability to segregate and retrieve only synchronous data, ie., data stored at predetermined timed intervals, as well as to segregate and retrieve only asynchronous data, ie., data stored as a result of non-scheduled or randomly occurring events.